Temperature and pressure dual-mode decoupling flexible sensor based on full resistance type response mechanism

Abstract

The invention belongs to the technical field of flexible sensors, and particularly relates to a temperature-pressure dual-mode decoupling flexible sensor based on a full resistance type response mechanism. The invention discloses a preparation method of a dual-mode decoupling flexible sensor capable of simultaneously detecting a temperature signal and a pressure signal, the sensor comprises a five-layer structure, the upper layer and the lower layer are PET packaging layers coated with silver electrodes, and the middle structure is formed by stacking a pressure sensor, a silver electrode and a temperature sensor in sequence from top to bottom. The temperature-sensitive material and the pressure-sensitive material in the dual-function sensor are both in a resistance response mechanism under stimulation, and signals are inevitably interfered. For the pressure sensor, the pressure sensor shows positive temperature coefficient response, and the response to the temperature is close to zero by adding a material with a negative temperature coefficient, so that the pressure sensor is insensitive to a temperature signal. For the temperature sensor, the pressure signal desensitization of the temperature sensor is realized through the preparation of an ultrathin temperature sensing film material and the design of a dual-function sensor stacking mode. By adjusting the sensor film to be sensitive to only one stimulus and negligible in response to the other stimulus, decoupling of temperature and pressure signals is achieved, the temperature and the pressure can be detected and distinguished at the same time, a resistance signal serves as a unique output signal, a complex signal processing and reading system is not needed, the preparation process is simple, and operability is high. And the manufactured sensor is high in sensitivity and is applied to the fields of wearable equipment, man-machine interaction, electronic skin, bionic robots and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and in particular relates to a temperature-pressure dual-mode decoupling flexible sensor based on a full-resistance response mechanism. Background Art

[0002] In recent years, flexible multifunctional sensors that can detect important physical stimuli such as pressure and temperature have become a research hotspot due to their application prospects in flexible electronics, prosthetic development, soft robotics and medical devices. In order to monitor more than one physical stimulus at the same time, multifunctional sensor devices should be able to detect and decouple multiple stimulus sources without interfering with each other. At present, a large number of studies have achieved sensor temperature and pressure signal decoupling by converting temperature and pressure stimuli into independent electrical signals using different sensing mechanisms. Generally speaking, the working mechanism of temperature sensors is mainly thermal resistance and thermoelectric effect, which can convert temperature into resistance and voltage signals respectively. The main working mechanism of pressure sensors is piezoresistance, piezocatrix and piezoelectric / triboelectric effect, which converts pressure into resistance, capacitance and voltage signals respectively, but this inevitably requires the use of complex signal processing and readout systems to analyze the current-voltage output of the sensor, hindering their widespread commercial application.

[0003] In order to solve the above problems, we started from the aspects of structural design, material selection and process preparation, and proposed a temperature and pressure dual-mode decoupled flexible sensor based on a fully resistive response mechanism. The sensor is composed of a pressure sensor based on the piezoresistive effect and a temperature sensor based on the thermal resistance effect by simply stacking up and down. The flexible porous pressure sensor based on the multi-level structure carbon material of reduced graphene oxide / carbon nanocoil is highly sensitive to pressure and has little sensitivity to temperature. The CNF flexible temperature sensor based on carbon nanofibers has a good temperature response but is insensitive to pressure stimulation, thereby realizing the decoupling of temperature and pressure signals without the need for complex signal processing and readout systems. The preparation process is simple and the operability is strong. Summary of the invention

[0004] In view of this, the present invention aims to provide a temperature-pressure dual-mode decoupled flexible sensor based on a fully resistive response mechanism. The temperature-pressure dual-mode sensor provided by the present invention uses a resistance signal as the only output signal, and does not require a complicated signal processing and readout system while identifying temperature and pressure stimuli. The sensor preparation process is simple and has strong operability.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A temperature-pressure dual-mode decoupled flexible sensor based on a fully resistive response mechanism, the sensor comprising a 5-layer structure, wherein the upper and lower layers are both PET packaging layers coated with silver electrodes, and the middle structure is stacked from top to bottom with a pressure sensor, a silver electrode, and a temperature sensor.

[0007] Furthermore, the pressure sensing layer is a flexible porous pressure sensor based on reduced graphene oxide / carbon nanocoil multi-level structure carbon material, which responds to pressure stimulation based on a piezoresistive working mechanism, and its response to temperature stimulation is negligible by adding a material with a negative temperature coefficient.

[0008] Furthermore, the temperature sensing layer is a carbon nanofiber membrane obtained by electrospinning, which responds to temperature stimulation based on a resistive working mechanism, and is desensitized to pressure stimulation by preparing an ultra-thin structure and a bottom layer design of a dual-function sensor device.

[0009] Furthermore, the PET packaging layer with the silver electrode coated on the surface is obtained by screen printing.

[0010] The present invention also provides a method for preparing a temperature-pressure dual-mode decoupling flexible sensor based on a full-resistance response mechanism, comprising the following steps:

[0011] S1. Preparation of pressure sensor: Weigh and prepare the graphene oxide aqueous dispersion slurry, polyvinyl pyrrolidone PVPK30, sodium cholate, nickel chloride hexahydrate, ferric chloride hexahydrate and urea in a certain proportion, add deionized water to 60 ml, and after magnetic stirring and ultrasonic treatment, transfer to a polytetrafluoroethylene hydrothermal reactor for insulation reaction at 120°C for 10 h. After natural cooling, the obtained precipitate was washed three times with deionized water and alcohol respectively, and freeze-dried to obtain reduced graphene oxide powder loaded with nickel-iron bimetallic catalyst precursor. The reduced graphene oxide powder loaded with nickel-iron bimetallic catalyst precursor was spread flat in a quartz boat, placed in a tube furnace, annealed at 500°C for 3 h in an inert gas atmosphere, and then hydrogen was introduced and the temperature was continued to rise to 700°C. After the temperature stabilizes, the hydrogen is turned off, the carbon source is introduced, the gas flow rate is set to 30 sccm, the reaction is carried out at 700 °C for 1 h, and the reduced graphene oxide / carbon nanocoil multi-level structure carbon material is cooled to room temperature to obtain the reduced graphene oxide / carbon nanocoil multi-level structure carbon material. The obtained reduced graphene oxide / carbon nanocoil multi-level structure carbon material is dispersed in deionized water, placed in a flexible porous foam material, ultrasonically treated for 1 h, placed in an oven for drying, cut into a certain size, and the upper and lower electrodes are added to obtain a flexible pressure sensor based on the reduced graphene oxide / carbon nanocoil multi-level structure carbon material.

[0012] S2. Preparation of temperature sensor: The precursor solution obtained by dissolving 10 wt% PAN in DMF was magnetically stirred at 80 °C for 3 h to obtain the precursor polymer. The electrospinning machine was operated at 16 kV, and the distance between the spinning needle and the collector was kept constant. The flow rate was maintained at 0.2 mL h −1 , on the drum collector at 0.5 m min -1The PAN nanofiber membrane was prepared at a rotation speed of 100 rpm. During the spinning process, the relative humidity was kept below 40%. The PAN nanofiber membrane was then stabilized in an oven at 230 °C for 3 h and then heated at 550 °C in an inert atmosphere at 2 °C min -1 The carbon nanofiber membrane was carbonized at a rate of 1 h to obtain a carbon nanofiber membrane. A layer of PDMS was coated on both sides of the prepared carbon nanofiber membrane and upper and lower electrodes were added to obtain a CNF flexible temperature sensor.

[0013] S3. Prepare a PET encapsulation layer coated with silver electrodes: place a screen printing plate on a PET film, then place a certain amount of evenly stirred conductive silver paste in the screen frame of the screen printing plate, use a scraper to apply the conductive silver paste evenly on the PET film, and cure it at 120°C for 2 h to obtain a PET encapsulation layer coated with silver electrodes.

[0014] S4. Prepare a dual-function sensor: assemble the temperature sensor, the pressure sensor and the PET packaging layer coated with silver electrodes in sequence from bottom to top to obtain the temperature and pressure dual-mode sensor.

[0015] The present invention also provides a wearable device comprising at least one dual-mode sensor disclosed above.

[0016] Compared with the prior art, the temperature and pressure dual-mode decoupling flexible sensor based on a full-resistance response mechanism described in the present invention has the following advantages:

[0017] First, the dual-function sensor of the present invention uses resistance as the only output signal, can simultaneously identify temperature and pressure stimulation without complex signal processing and readout systems, and has good response to external stimulation and high sensitivity.

[0018] Second, the present invention successfully prepares a pressure sensor with good pressure sensitivity and close to zero temperature response by using a material with a negative temperature coefficient to regulate the pressure membrane material showing a positive temperature coefficient effect.

[0019] Third, the present invention uses an electrospinning method to prepare a temperature-sensitive membrane material with an ultra-thin structure, and desensitizes the temperature-sensitive membrane to pressure signals by stacking a pressure sensor, a silver electrode, and a temperature sensor in sequence on a bottom layer.

[0020] Fourth, the carbon nanofiber membrane, carbon nanocoil, flexible porous foam, etc. used to make the sensor have good skin compatibility, can be in direct contact with skin tissue, and the preparation process is simple, efficient and highly operational. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the preparation process of the dual-function sensor of the present invention.

[0022] Figure 2 This is a SEM image of the multi-level structure of the pressure sensitive layer of the dual-function sensor of the present invention.

[0023] Figure 3 This is a physical picture of the temperature sensing layer film material of the present invention.

[0024] Figure 4 It is a schematic diagram of the pressure response performance test of the pressure sensor of the present invention.

[0025] Figure 5 It is a schematic diagram of the temperature response performance test of the temperature sensor of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention and the drawings of the specification to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The embodiment of the invention discloses a method for preparing a dual-function flexible sensor.

[0028] In order to better understand the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as a limitation of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above invention content are also considered to fall within the protection scope of the present invention.

[0029] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0030] Embodiment 1:

[0031] According to the method for preparing the dual-function flexible sensor of the present invention, this embodiment describes the specific preparation process thereof:

[0032] S1. Preparation of pressure sensor: Weigh and prepare the graphene oxide aqueous dispersion slurry, polyvinyl pyrrolidone PVPK30, sodium cholate, nickel chloride hexahydrate, ferric chloride hexahydrate and urea in a certain proportion, add deionized water to 60 ml, and after magnetic stirring and ultrasonic treatment, transfer to a polytetrafluoroethylene hydrothermal reactor for insulation reaction at 120°C for 10 h. After natural cooling, the obtained precipitate was washed three times with deionized water and alcohol respectively, and freeze-dried to obtain reduced graphene oxide powder loaded with nickel-iron bimetallic catalyst precursor. The reduced graphene oxide powder loaded with nickel-iron bimetallic catalyst precursor was spread flat in a quartz boat, placed in a tube furnace, annealed at 500°C for 3 h in an inert gas atmosphere, and then hydrogen was introduced and the temperature was continued to rise to 700°C. After the temperature stabilizes, the hydrogen is turned off, the carbon source is introduced, the gas flow rate is set to 30 sccm, the reaction is carried out at 700 °C for 1 h, and the reduced graphene oxide / carbon nanocoil multi-level structure carbon material is cooled to room temperature to obtain the reduced graphene oxide / carbon nanocoil multi-level structure carbon material. The obtained reduced graphene oxide / carbon nanocoil multi-level structure carbon material is dispersed in deionized water, placed in a flexible porous foam material, ultrasonically treated for 1 h, placed in an oven for drying, cut into a certain size, and the upper and lower electrodes are added to obtain a flexible pressure sensor based on the reduced graphene oxide / carbon nanocoil multi-level structure carbon material.

[0033] S2. Preparation of temperature sensor: The precursor solution obtained by dissolving 10 wt% PAN in DMF was magnetically stirred at 80 °C for 3 h to obtain the precursor polymer. The electrospinning machine was operated at 16 kV, and the distance between the spinning needle and the collector was kept constant. The flow rate was maintained at 0.2 mL h −1 , on the drum collector at 0.5 m min -1 The PAN nanofiber membrane was prepared at a rotation speed of 100 rpm. During the spinning process, the relative humidity was kept below 40%. The PAN nanofiber membrane was then stabilized in an oven at 230 °C for 3 h and then heated at 550 °C in an inert atmosphere at 2 °C min -1 The carbon nanofiber membrane was carbonized at a rate of 1 h to obtain a carbon nanofiber membrane. A layer of PDMS was coated on both sides of the prepared carbon nanofiber membrane and upper and lower electrodes were added to obtain a CNF flexible temperature sensor.

[0034] S3. Prepare a PET encapsulation layer coated with silver electrodes: place a screen printing plate on a PET film, then place a certain amount of evenly stirred conductive silver paste in the screen frame of the screen printing plate, use a scraper to apply the conductive silver paste evenly on the PET film, and cure it at 120°C for 2 h to obtain a PET encapsulation layer coated with silver electrodes.

[0035] S4. Prepare a dual-function sensor: assemble the temperature sensor, the pressure sensor and the PET packaging layer coated with silver electrodes in sequence from bottom to top to obtain the temperature and pressure dual-mode sensor.

[0036] Furthermore, the temperature sensing layer of the dual-function flexible sensor described in the first embodiment of the present invention is made of a PAN precursor solution through an electrospinning process, and the specific configuration process is as follows:

[0037] First, 1 g of PAN was weighed, 10 ml of DMF solution was added, and magnetic stirring was performed at 80 °C for 3 h to fully dissolve and mix evenly to obtain a 10 wt % PAN DMF electrospinning precursor solution.

[0038] Furthermore, the pressure sensing layer of the dual-function flexible sensor described in the first embodiment of the present invention is composed of a carbon material based on a multi-level structure of reduced graphene oxide / carbon nano coils, which is prepared by hydrothermal reaction of graphene slurry and then CVD high-temperature reduction calcination. The specific configuration process is as follows:

[0039] Weigh 20g of graphene oxide aqueous dispersion slurry (purity 2wt%), 0.2g of polyvinyl pyrrolidone PVPK30, and 0.12g of sodium cholate, add deionized water to 60ml, shear and stir for 1 h~2 h, and ultrasonically treat for 30 min~1 h to obtain a uniformly dispersed GO solution. Then add 3mmol of nickel chloride hexahydrate, 1mmol of ferric chloride hexahydrate, and 0.72g of urea to the GO solution, shear and stir for 1 h~2 h, and ultrasonically treat for 30 min~1 h to obtain a hydrothermal reaction slurry.

[0040] In addition, in order to further illustrate the superiority of the technology of the present invention, the inventors also conducted the following experiment, which demonstrated the key performance parameters of the dual-function flexible sensor prepared in Example 1.

[0041] Figure 4 The pressure sensing performance of the dual-function flexible sensor of the present invention at 0-100Kpa is demonstrated, wherein the pressure sensitive unit used is a flexible porous foam loaded with reduced graphene oxide / carbon nanocoil multi-level structure carbon material. Figure 4 It can be seen that after applying different pressures to the sensor, the sensor shows different resistance signal responses and the sensor shows high sensitivity to pressure stimulation. In practical applications, it can accurately capture subtle activity signals of the human body, such as breathing and pulse.

[0042] Figure 5 The temperature sensing performance of the dual-function flexible sensor of the present invention is demonstrated. Figure 5It can be seen that at different temperatures, the sensor exhibits different resistance signal responses. The resistance change rate of the sensor shows a highly linear relationship with temperature, proving that the dual-function flexible sensor can accurately capture the temperature changes of the human body in practical applications.

[0043] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A temperature and pressure dual-mode decoupling flexible sensor based on a fully resistive response mechanism, characterized in that: The sensor includes a five-layer structure, wherein the upper and lower layers are both PET packaging layers coated with silver electrodes, and the middle structure includes a pressure sensor, a silver electrode / PET packaging layer, and a temperature sensor from top to bottom.

2. According to claim 1, a temperature and pressure dual-mode decoupling flexible sensor based on a full resistive response mechanism is characterized by: The pressure sensing layer is a flexible porous pressure sensor based on reduced graphene oxide / carbon nanocoil multi-level structure carbon material, which responds to pressure stimulation based on a piezoresistive working mechanism, and its response to temperature stimulation is negligible by adding a material with a negative temperature coefficient.

3. According to claim 1, a temperature and pressure dual-mode decoupling flexible sensor based on a full resistive response mechanism is characterized in that: The temperature sensitive layer is a carbon nanofiber membrane obtained by electrospinning, which responds to temperature stimulation based on a resistive working mechanism, and is desensitized to pressure stimulation by preparing an ultra-thin structure and a bottom layer design of a dual-function sensor device.

4. According to claim 1, a temperature and pressure dual-mode decoupling flexible sensor based on a full resistive response mechanism is characterized by: The PET packaging layer with the silver electrode coated on the surface is obtained by screen printing.

5. A method for preparing a temperature-pressure dual-mode decoupling flexible sensor based on a full resistive response mechanism according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Preparation of pressure sensor: Weigh and prepare the graphene oxide aqueous dispersion slurry, polyvinyl pyrrolidone PVPK30, sodium cholate, nickel chloride hexahydrate, ferric chloride hexahydrate and urea in a certain proportion, add deionized water to 60 ml, and after magnetic stirring and ultrasonic treatment, transfer to a polytetrafluoroethylene hydrothermal reactor for insulation reaction at 120 ° C for 10 h. After natural cooling, the obtained precipitate was washed three times with deionized water and alcohol respectively, and freeze-dried to obtain reduced graphene oxide powder loaded with nickel-iron bimetallic catalyst precursor. The reduced graphene oxide powder loaded with nickel-iron bimetallic catalyst precursor was spread flat in a quartz boat, placed in a tube furnace, annealed at 500 ° C for 3 h in an inert gas atmosphere, and then hydrogen was introduced and the temperature was continued to rise to 700 ° C. After the temperature stabilizes, the hydrogen is turned off, the carbon source is introduced, the gas flow rate is set to 30 sccm, the reaction is carried out at 700 °C for 1 h, and the reaction is cooled to room temperature to obtain a reduced graphene oxide / carbon nanocoil multi-level structure carbon material. The obtained reduced graphene oxide / carbon nanocoil multi-level structure carbon material is dispersed in deionized water, placed in a flexible porous foam material, ultrasonically treated for 1 h, placed in an oven for drying, cut into a certain size, and the upper and lower electrodes are added to obtain a flexible pressure sensor based on reduced graphene oxide / carbon nanocoil multi-level structure carbon material; S2. Preparation of temperature sensor: The precursor solution obtained by dissolving 10 wt% PAN in DMF was magnetically stirred at 80 °C for 3 h to obtain the precursor polymer. The electrospinning machine was operated at 16 kV, and the distance between the spinning needle and the collector was kept constant. The flow rate was maintained at 0.2 mL h −1 , on the drum collector at 0.5 m min -1 The PAN nanofiber membrane was prepared at a rotation speed of 100 rpm. During the spinning process, the relative humidity was kept below 40%. The PAN nanofiber membrane was then stabilized in an oven at 230 °C for 3 h and then heated at 550 °C in an inert atmosphere at 2 °C min -1 The carbon nanofiber membrane was carbonized at a rate of 1 h to obtain a carbon nanofiber membrane. A layer of PDMS was coated on both sides of the obtained carbon nanofiber membrane and upper and lower electrodes were added to obtain a CNF flexible temperature sensor. S3. Prepare a PET encapsulation layer coated with silver electrodes: place a screen printing plate on a PET film, then place a certain amount of stirred conductive silver paste in the screen frame of the screen printing plate, use a scraper to apply the conductive silver paste evenly on the PET film, and cure it at 120°C for 2 h to obtain a PET encapsulation layer coated with silver electrodes; S4. Prepare a dual-function sensor: assemble the temperature sensor, the pressure sensor and the PET packaging layer coated with silver electrodes in sequence from bottom to top to obtain the temperature and pressure dual-mode sensor.

6. The method for preparing a temperature-pressure dual-mode decoupling flexible sensor based on a full resistive response mechanism according to claim 5, characterized in that: The purity of the graphene oxide aqueous dispersion slurry described in S1 is 2 wt %.

7. The method for preparing a temperature-pressure dual-mode decoupling flexible sensor based on a full-resistance response mechanism according to claim 5, characterized in that: The flexible porous foam material described in S1 is PDMS foam, and a material having a negative temperature coefficient which is opposite to the temperature response of the pressure membrane material is added therein.

8. The method for preparing a temperature-pressure dual-mode decoupling flexible sensor based on a full resistive response mechanism according to claim 5, characterized in that: The electrospinning precursor solution preparation process of S2 is as follows: first, 1 g of PAN polyacrylonitrile is weighed, 10 ml of DMF solution is added thereto, and magnetic stirring is performed at 80 °C for 3 h to fully dissolve and mix the solution evenly, thereby obtaining a 10 wt % PAN DMF electrospinning precursor solution.

9. The method for preparing a temperature-pressure dual-mode decoupling flexible sensor based on a full resistive response mechanism according to claim 5, characterized in that: The distance between the spinning needle and the collector described in S2 was kept constant at 150 mm.

10. Application of the flexible dual-mode sensor prepared by the method for preparing the temperature-pressure dual-mode decoupling flexible sensor based on a full-resistive response mechanism as described in any one of claims 1 to 9 in electronic skin or environmental detection.

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